In 2016 the U.S. EPA began phasing in Tier 3 Gasoline, mandating the maximum allowable sulfur in gasoline to be 10 ppm (10 mg/kg). PBMS testing requirements similar to those for Ultra-Low Sulfur Diesel (ULSD) were established. The EPA allows any testing method that can comply with the performance guidelines for accuracy and precision.

For the analysis described in the report, empirical calibrations were built using a suite of six commercially available certified gasoline calibration standards. The detection limits were determined by the empirical method, whereby ten repeat analyses of a blank gasoline sample containing 0.0 ppm S were taken with the sample in static position and the standard deviation determined. The Lower Limits of Detection (LLD), defined as three times the standard deviation, were reported as 0.24 ppm for Tier 3 gasoline using a measurement time of 300 sec per analysis.

The analysis was performed using the Rigaku NEX CG monochromatic EDXRF spectrometer, using Cartesian Geometry polarization. Ideally suited for ultra-low sulfur measurements, such as those for Tier 3 Gasoline and ULSD, the NEX CG spectrometer is a multi-element analyzer capable of performing a variety of applications throughout the petroleum industry, including down-stream analyses as well as mid-stream and upstream measurements.

The results detailed in the report demonstrate that the NEX CG analyzer complies with U.S. EPA Tier 3 Gasoline performance-based testing protocols and achieves this excellent performance using monochromatic EDXRF with Cartesian Geometry polarization.

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